What do you mean with "patch release"? FoV is a new product. It's an add-on you have to purchase. There will probably be a release on the usual download platforms, but as always you are well advised to buy the add-on on the same platform as the main game. So if you bought retail you should also get FoV retail, to avoid incompatibilities.
Btw, FoV is significantly better than Divinity 2 vanilla, IMHO. I finished it this week. The more compact design and the (quite harmless) monster respawn in dungeons and enemy territory give FoV a different rhythm.
